This study wil utilize newly developed monoclonal antibodies against free beta hCG and intact hCG to determine if malignant sequelae of hydatidiform mole can be predicted at initial diagnosis. Patients from the Southern Trophoblastic Disease Center will be studied. Radioimmunoassays for free beta hCG and intact hCG will be performed at the time of diagnosis to determine whether the ratio of free beta hCG to total hCG may be of value in predicting which molar pregnancies will develop persistent disease. Then serial serum and urinary assays will be performed in order to characterize the regression curve of free beta hCG. This will establish the time period available to demonstrate free beta hCG as an indicator of persistent trophoblastic disease. Immunohistochemical studies utilizing the free beta and intact hCG monoclonal antibodies will be performed on the initial molar tissue to define the site of secretion and to correlate this with histologic appearance of the mole. If the study is successful in predicting the 20% of patients who will develop persistent trophoblastic disease, prophylactic chemotherapy could be given leading to a significant reduction in malignant sequelae and a substantial savings in money and morbidity for patients with molar pregnancy. (3)